Mostrando ítems 1-20 de 33

Carbazole-Based Hyperbranched Polyester Polyol: Structural, Rheological, Thermal and Optical Properties

Murillo, Edwin A.; Percino, M. Judith; Ceron, Margarita (Macromolecular Research, 2021-04-24)

The present study sought to obtain a hyperbranched polyester polyol derivative with fluorescent properties. Initially, a 4-((4-(9H-carbazol-9-yl)benzyl)oxy)-4-oxobut-2-enoic acid (CAV) was synthesized and esterified with ...
Colloidal, morphological, thermal, rheological, and film properties of waterborne hyperbranched alkyd¿acrylic resins

Murillo, Edwin A.; Lopez, Betty; Percino, M. Judith (Journal of Coatings Technology Research, 2019-04-23)

Waterborne hyperbranched alkyd–acrylic resins (HAAR) are interesting materials that provide excellent properties yet require only low levels of solvent in formulations using them. However, they have been scarcely studied. ...
Comb-shaped silicone-alkyd resins with high solid content

Mejía, María C.; Palacio, Juliana; Murillo, Edwin A. (Progress in Organic CoatingsWashintong D.C , Estados Unidos, 2017-04)

An unique com-shaped silicone-alkyd resins (SiAR) were synthesized with high solid content (65 wt%) prepared from an alkyd resin (AR) and a varying weight% (5, 10, 15, 20) of silicone moiety (Z-6018) by etherification ...
Compatibilization of LDPE/PA6 by Using a LDPE Functionalized with a Maleinized Hyperbranched Polyester Polyol

Ararat, Carlos A.; Percino, M. Judith; Murillo, Edwin A. (Macromolecular Research, 2019-11-12)

Low density polyethylene (LDPE)/polyamide6 (PA) blends can lead to a synergy between the properties of these materials. These blends are employed mainly in the packing industry, especially in food factories. The problem ...
Effect of Calcination Temperature on the Behavior of the Agglomerated Co3O4 Nanoparticles Obtained Through the Sol–Gel Method

Raba, Angela; Cardenas-Flechas, L. J.; Barba-Ortega, J.; Rincón Joya, Miryam; Moreno-Aldana, Luis Carlos (Journal of Inorganic and Organometallic Polymers and MaterialsWashintong D.C , Estados Unidos, 2020-07-31)

gglomerates of Co3O4 were obtained using the sol–gel method for the synthesis with subsequent calcination of the samples up to 550 °C. Through X-rays it was observed that the samples presented the pure spinel phase with a ...
Effect of tungsten doping on the structural, morphological and bactericidal properties of nanostructured CuO

Raba, Angela; Malafatti, João Otávio Donizette; Parra-Vargas, Carlos Arturo; Paris, Elaine Cristina; Rincón Joya, Miryam (PLOS ONEWashintong D.C , Estados Unidos, 2020-09-28)

Copper oxide (CuO) has been broadly used in different technological and biological applications. However, based on the literature review, there are few reports describing the synthesis of tungsten doped copper oxide and ...
Effects of metal doping agent on the properties of Nb2−xMxO5 (M = Mn, Fe, and Ni) system

Raba, Angela; Barba, Jose; Rincón Joya, Miryam (International Journal Of Applied Ceramic TechnologyBogota , Colombia, 2018-05-21)

In order to improve the behavior Niobium pentoxide on oxidation-reductionreactions to degrade organic compounds in aqueous solutions, we developed the synthesis of Niobium pentoxide with the metal doping agents: manganese,iron, ...
Evaluation of a hyperbranched polyester polyol as plasticizing agent for composites of recycled polystyrene and rice husk

Murillo Ruiz, Edwin Alberto; Sandova, N A; Cruz, A P (Journal of Physics: Conference Series, 2020-08-05)

This study makes a contribution to the preparation of composites from recycled polystyrene and rice husk (it is mainly incinerated producing environmental contamination in Norte de Santander department-Colombia), which ...
Evaluation of the effect of a hyperbranched polyester on the thermal, rheological, morphological and mechanical properties of polyvinyl chloride/hemp fiber blends

Tolosa Ayala, Roger Jampier; Murillo Ruiz, Edwin Alberto (Journal of Physics: Conference SeriesReino Unido, 2019-11-29)

The aim of this study was to investigate the effect of the hyperbranched polyester polyol from second generation content on the structural, thermal, rheological, morphological and mechanical properties of recycled polyvinyl ...
Evaluation of the rheological properties in solution and molten state of hyperbranched polyester polyols obtained of first and second generation

Murillo Ruiz, Edwin Alberto (Journal of Physics: Conference Series, 2020-08-05)

The hyperbranched polyesters have gain great attention since these materials have smallest hydrodynamic dimensions, high functionality, good solubility and they may be modified for obtaining compounds for specific applications. ...
Evaluation of the structural, thermal, rheological and morphological properties of polyethylene functionalized with a maleinized hyperbranched polyester

Ararat Bermudez, Carlos Alberto; Murillo Ruiz, Edwin Alberto (Journal of Physics: Conference Series, 2019-11-29)

This experimental study was carried out with the aim of establishing and analyzing the thermal, structural, morphological, and rheological properties of a polyethylene functionalized with a maleinized hyperbranched polyester. ...
Functionalization in solution of polypropylene with a maleinized hyperbranched polyol polyester: Structural, thermal, rheological, and mechanical properties

Nova, María; Arévalo, Yaritza; Murillo, Edwin A. (Journal of Applied Polymer ScienceWashintong D.C , Estados Unidos, 2018-07-18)

The functionalization of polypropylene (PP) with a maleinized hyperbranched polyester polyol (MHBP) was performed in solution to obtain PP-g-MHBPs. The degree of functionalization (FD) increased with MHBP and dicumyl ...
HYPERBRANCHED ALKYD RESINS OBTAINED FROM A HYPERBRANCHED POLYESTER POLYOL OF THE FIFTH GENERATION AND TALL OIL FATTY ACID

Murillo Ruiz, Edwin Alberto; Raba Paez, Angela Mercedes (Rasayan Journal of Chemistry, 2023-09)

The first aim of this study was to synthesize hyperbranched alkyd resins from tall oil fatty acids and a hyperbranched polyester polyol via an esterification reaction. The second aim was to evaluate the effect of the fatty ...
Hyperbranched polyester polyol modified with polylactic acid as a compatibilizer for plasticized tapioca starch/polylactic acid blends

Murillo Ruiz, Edwin Alberto; Mesias Alvarez, Ricardo Esteban (PolimerosBrasilia, Brasil, 2018-03-15)

A hyperbranched polyester polyol of the second generation (HBP2) was modified with polylactic acid (HBP2-g-PLA) and employed as a compatibilizer for plasticized tapioca starch (TPS)/polylactic acid (PLA) blends. The effect ...
Hyperbranched polyester polyol plasticized tapioca starch/low density polyethylene blends

Guzman, Manuel; Giraldo, Diego; Murillo, Edwin A. (PolimerosBrasilia , Brasil, 2017)

In this work, low density polyethylene (LDPE)/plasticized starch (TPS) blends were prepared. The TPS employed in this study was obtained by plasticization of tapioca starch with a hyperbranched polyester polyol. Differential ...
Influence of the H2O content and the time on the formation of nanostructures in a chemical solution of H2O/HF/NH4F/EG

Raba, Angela; Bautista-Ruiz, Jorge; Rincón Joya, Miryam (Journal of Physics: Conference Series, 2018-12-07)

The influence of anodizing time on the length, morphology and photoelectrochem-ical properties of TiO2 Nanotubes has been investigated. An optimum anodizing time of 20 min at 20V leads to 220nm long of the nanotubes. By ...
Maleinized Hyperbranched Polyol Polyester: Effect of the Content of Maleic Anhydride in the Structural, Thermal and Rheological Properties

Ararat, Carlos A.; Quiñonez, Winston; Murillo, Edwin A. (Macromolecular Research, 2019-03-29)

The aim of this work is to obtain the material that, in the future, may become a better alternative, as a functionalizing agent, to maleic anhydride (MA), or a crosslinking agent with the least amount of functional groups. ...
Mn-modification effects on Nb2O5 structural, optical and vibrational properties

Raba, Angela; Murillo, Edwin A.; Rincón Joya, Miryam (Journal of Physics: Conference SeriesWashintong D.C , Estados Unidos, 2017-12-29)

In this study Mn-modification (at 1%, 2.5%, 5% and 10%) on Nb2O5 was carried out through the Pechini method; the annealing temperatures: 400°C, 500°C, 600°C and 700°C, were used to study the thermal stability of the system ...
Niobium Pentoxide Samples with Addition of Manganese at Different Concentrations and Calcination Temperatures Applied in the Photocatalytic Degradation of Rhodamine B

Raba, Angela; Falcony, Ciro; Supelano, Ivan; Rincón Joya, Miryam (Applied SciencesBerna , Suiza, 2020-06-21)

In order to improve the photocatalytic effect of Nb2O5, manganese from 1% to 10% was added by the polymeric precursor’s method. The samples obtained were subjected to different calcination temperatures from 400 to 700 °C. ...
Polietileno de baja densidad funcionalizado con un poliéster poliol altamente ramificado maleinizado

Murillo, Edwin A.; Ararat, Carlos A. (Ingeniería Y CienciaBogota , Colombia, 2016-02-22)

En este trabajo, polietileno de baja densidad (PEBD) fue modificado en estado fundido con un poliester poliol altamente ramificado maleinizado (HBPAM), usando varias proporciones de peróxido de dicumilo (0.5, 1.0, 1.5 ...

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Carbazole-Based Hyperbranched Polyester Polyol: Structural, Rheological, Thermal and Optical Properties
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Murillo, Edwin A. | 2021-04-24

The present study sought to obtain a hyperbranched polyester polyol derivative with fluorescent properties. Initially, a 4-((4-(9H-carbazol-9-yl)benzyl)oxy)-4-oxobut-2-enoic acid (CAV) was synthesized and esterified with a hyperbranched polyester polyol obtained from fourth generation (HBP) to synthesize carbazole-based hyperbranched polyester polyols (HBPCAV). The proportions employed of CAV were 5, 10, 15, and 20 wt% relative to that of HBP. The grafted CAV percentage (PgCAV) increased with the CAV content. The conversion percentages (CP) of the reactions for obtaining HBPCAV were higher than 95% and the hydroxyl values (OHV) were lower than that of HBP. The modification percentage (MP) of the HBP was between 9.33 and 27.38%. Using proton nuclear magnetic resonance (1H NMR) and infrared (IR) analyses was evidenced the formation of CAV and HBPCAV. Dynamic light scattering (DLS) analysis showed that HBPCAV exhibited aggregations. The number average molar mass (Mn), viscosity (η), and glass transition temperature (Tg) values of the HBPCAV samples were higher than those of the HBP, and also increased with the PgCAV values. The rheological behaviors of the HBP and HBPCAV samples were mainly Newtonian and shear-thinning, respectively. All HBPCAV exhibited electroluminescent properties.

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Colloidal, morphological, thermal, rheological, and film properties of waterborne hyperbranched alkyd¿acrylic resins
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Murillo, Edwin A. | 2019-04-23

Waterborne hyperbranched alkyd–acrylic resins (HAAR) are interesting materials that provide excellent properties yet require only low levels of solvent in formulations using them. However, they have been scarcely studied. Therefore, the goal of this work was to prepare and evaluate various properties of HAAR. These materials were obtained by miniemulsion polymerization from a hyperbranched alkyd resin (HAR), methyl methacrylate (MMA), butyl acrylate (BA), and acrylic acid (AA). The proportions of HAR:acrylic monomers were as follow: 50:50 (HAAR1), 40:60 (HAAR2), 30:70 (HAAR3), and 20:80 (HAAR4). The particle size increased with the content of HAR, but the colloidal stability, critical deformation, zeta potential, thermal stability, and hardness followed an opposite behavior. The order of colloidal stability of the HAAR miniemulsions was HAAR4 > HAAR3 > HAAR2 > HAAR1. The particle morphology of the HAAR was mainly core–shell, but acrylic and alkyd particles were also observed. In addition, all HAAR initially exhibited a reduction in complex viscosity (η*) with the increase in angular frequency. The thermal stability of the HAR was lower than that of the HAAR. The HAAR showed better resistance against a 0.10 M sodium hydroxide (NaOH) solution than HAR.

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Comb-shaped silicone-alkyd resins with high solid content
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Mejía, María C. | 2017-04

An unique com-shaped silicone-alkyd resins (SiAR) were synthesized with high solid content (65 wt%) prepared from an alkyd resin (AR) and a varying weight% (5, 10, 15, 20) of silicone moiety (Z-6018) by etherification reaction. The viscosity and the hydroxyl value (OHV) of the SiAR were found to be higher than those of the AR. The formation of the SiAR was confirmed by infrared spectroscopy and mass spectrometry analysis. The glass transition temperature (Tg), thermal stability, and molecular weight of the SiAR, increased with increasing the silicone content and compared with those of the AR. The results of chemical resistance showed that the SiAR exhibited a better resistance than AR against 0.1 M sodium hydroxide (NaOH) solution.

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Compatibilization of LDPE/PA6 by Using a LDPE Functionalized with a Maleinized Hyperbranched Polyester Polyol
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Ararat, Carlos A. | 2019-11-12

Low density polyethylene (LDPE)/polyamide6 (PA) blends can lead to a synergy between the properties of these materials. These blends are employed mainly in the packing industry, especially in food factories. The problem of this system is that it is inmiscible, hence requires to be compatibilized. The aim of this study is to compatibilize blends of LDPE/PA6 using a LDPE modified with a maleinized hyperbranched polyol polyester (LDPE-g-MHBP) as a compatibilizing agent. Therefore blends of LDPE (50 wt%)/PA (50 wt%) were prepared by using proportions of 5 (Blend5), 10 (Blend10), 15 (Blend15) and 20 (Blend20) wt% of the LDPE-g-MHBP of the total mix. On the other hand, to determine the efficiency of the LDPE-g-MHBP as a compatibilizing agent, a Blend0 (blends of LDPE (50 wt%)/PA (50 wt%) without LDPE-g-MHBP) was used as the control sample. By infrared (IR) analysis was evidenced the interactions between PA and LDPE-g-MHBP. By differential scanning calorimetry analysis (DSC) was observed that the LDPE-g-MHBP increased the crystallinity of the LDPE phase, but the behavior was opposite to PA. The thermal stability and the viscosity of the blends obtained with LDPE-g-MHBP were higher than those of the Blend0. Scanning electron microscopy (SEM) analysis revealed that the LDPE-g-MHBP ostensibly improved the miscibility of the LDPE/PA blends.

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Effect of Calcination Temperature on the Behavior of the Agglomerated Co3O4 Nanoparticles Obtained Through the Sol–Gel Method
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Raba, Angela | 2020-07-31

gglomerates of Co3O4 were obtained using the sol–gel method for the synthesis with subsequent calcination of the samples up to 550 °C. Through X-rays it was observed that the samples presented the pure spinel phase with a crystallite size between 33.73 and 41.45 nm. In the thermogravimetric measurement from 262 °C high structural stability is presented with phase change at 917 °C. As the temperature increases, the particles increase in size, observing agglomerated nanometer particles that increase with temperature (3.5–3.8 μm). The 683 cm−1 Raman mode for 550 °C clearly presents an shifted compared to the other samples. The band gap for the samples under study varied with the temperature change of 1.77–1.81 eV. The FWHM decreases at a higher temperature, this confirms the larger crystallite size and the higher degree of sintering

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Effect of tungsten doping on the structural, morphological and bactericidal properties of nanostructured CuO
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Raba, Angela | 2020-09-28

Copper oxide (CuO) has been broadly used in different technological and biological applications. However, based on the literature review, there are few reports describing the synthesis of tungsten doped copper oxide and its biological applications, although CuO and W (tungsten) based nanomaterials have been reportedly already synthesized. In this study we synthesized novel CuO and CuO/W (at.1%, 2% and 4%) nanoparticles and explored their tungsten content-dependent bactericide activity. In order to obtain the materials, was used a co-precipitation method which is of low cost. The synthesized materials were characterized by x-ray diffraction (XRD); XRD results indicated that only the sample with at.1% of W presented pure Tenorite phase. Diffuse reflectance spectroscopy (DRS) allowed to obtain the band gap energy values; CuO/W (at.2%) sample exhibited the minimum value of 2.62 eV. Grains sizes ranging from 39.78 to 53.47 nm were established through field emission—scanning electronic microscopy (FE-SEM), and these sizes were confirmed by transmission electron microscopy (TEM). Doping with W also influenced the morphology obtained in all cases. BET (Brunauer, Emmett, Teller) analysis allowed to establish an increase in specific surface area and pore size with W doping. The particle size was determined by dynamic light scattering (DLS). The bactericidal properties were tested using well diffusion method for Escherichia coli and Staphylococcus aureus bacteria. Bactericide response of CuO nanoparticles was improved by the inclusion of W dopant into the CuO structure, leading to an expansion in the inhibition zone for the CuO/W (at.1%) sample; inhibition halo diameters were 1.5 and 12 mm for CuO and CuO/W (at.1%), respectively. Hence, it was possible to infer the remarkable importance of the crystalline phase, morphology, particle size and specific superficial area of the CuO/W (at.1%) nanoparticles in its bactericide performance. WO3 secondary phase affected the bactericide response of the materials obtained at at.2% and at.4% of tungsten conten

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Effects of metal doping agent on the properties of Nb2−xMxO5 (M = Mn, Fe, and Ni) system
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Raba, Angela | 2018-05-21

In order to improve the behavior Niobium pentoxide on oxidation-reductionreactions to degrade organic compounds in aqueous solutions, we developed the synthesis of Niobium pentoxide with the metal doping agents: manganese,iron, and nickel (Nb2−xMxO5), respectively, and analyzing its effects on the structural and vibrational properties. The synthesis of the Nb2−xMxO5 (M = Mn, Fe, and Ni; x = 0.02 and 0.05) was performed according the Pechini method, but before the annealing, the samples were submitted to Thermogravimetric analysis study showing better pre-calcination annealing temperatures at 500 and 700°C for the materials. Then, we performed the crystal structural analysis by X-ray Diffraction, obtaining crystallite sizes between 15 and 47 nm, the accurate size analysis was calculated by Scherrer equation. Structural analysis was also performed by IR spectroscopy to evaluate the vibrational modes of synthetized samples. The dopping effects were evaluated by UV-Vis spectrophotometry through the energy band gap values, showing that doped samples with manganese and iron had lower values than undoped, except the sample doped with nickel. However, samples doped with iron at 2.5% showed better photocatalytic performance.

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Evaluation of a hyperbranched polyester polyol as plasticizing agent for composites of recycled polystyrene and rice husk
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Murillo Ruiz, Edwin Alberto | 2020-08-05

This study makes a contribution to the preparation of composites from recycled polystyrene and rice husk (it is mainly incinerated producing environmental contamination in Norte de Santander department-Colombia), which will contribute to reduce the accumulation of waste derivatives from polymeric and rice industries in this region. Hence, the aim of this work was to use a hyperbranched polyester as plasticizing agent and to evaluate its influence on the properties of the composites. The proportions of the recycled polystyrene and rice husk were 60 wt% and 40 wt% respectively. In the case of the polyester, were employed amount of 10 wt%, 20 wt%, 30 wt% and 40 wt%. Also was prepared a control sample (0 % of polyester). The results of infrared analysis evidenced changes in the absorption of the hydroxy groups. The thermogravimetric analysis showed that the first thermal decomposition of the composites decreased with the polyester content, but it did not follow the same trend on mechanical properties. The results of scanning electronic microscopy analysis allowed evidence that the fracture mechanism of the composite was fragile. The viscosity of the control sample was lower than that of the composites obtained with the polyester.

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Evaluation of the effect of a hyperbranched polyester on the thermal, rheological, morphological and mechanical properties of polyvinyl chloride/hemp fiber blends
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Tolosa Ayala, Roger Jampier | 2019-11-29

The aim of this study was to investigate the effect of the hyperbranched polyester polyol from second generation content on the structural, thermal, rheological, morphological and mechanical properties of recycled polyvinyl chloride/hemp fiber/hyperbranched polyester polyol obtained from second generation blends. In all blends, the amounts of recycled polyvinyl chloride and hemp fiber were 70 wt% and 30 wt% respectively. The blends were obtained in a torque rheometer. The proportions of hyperbranched polyester polyol regards to those of the polyvinyl chloride and hemp fibers were 5 wt%, 10 wt%, 15 wt% and 20 wt%. Additionally, a recycled polyvinyl chloride/hemp fiber blend was prepared to be used as control blend. Infrared analysis was then used to evidence the interaction between components of the blends. The thermal stability of the recycled polyvinyl chloride/hemp fiber/hyperbranched polyester polyol blends was lower than that of the polyvinyl chloride. Furthermore, it was not observed a trend in the thermal behavior of the recycled polyvinyl chloride blends. Hyperbranched polyester polyol increased the glass transition temperature of the blends. Additionally, rheological analysis results indicated that the hyperbranched polyester polyol reduced the viscosity of the blends.

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Evaluation of the rheological properties in solution and molten state of hyperbranched polyester polyols obtained of first and second generation
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Murillo Ruiz, Edwin Alberto | 2020-08-05

The hyperbranched polyesters have gain great attention since these materials have smallest hydrodynamic dimensions, high functionality, good solubility and they may be modified for obtaining compounds for specific applications. There are few reports about the rheological properties on the solution and molten state of the hyperbranched polyesters polyols obtained of the first and second generation, especially those prepared from dimethyl propionic acid and pentaerythritol. Thus, the aim of this study is to evaluate the rheological properties in solution and molten state of these materials. Furthermore, the hydrodynamic dimensions by dynamic light scattering by using dimethyl formamide and dimethyl sulfoxide as solvents also were analyzed. The hydrodynamic dimensions on volume of the hyperbranched polyesters polyols obtained of second generation by using dimethyl formamide as solvent were greater than those of first generation, but the behavior was different when was used dimethyl sulfoxide as solvent. Furthermore, these materials exhibited aggregations. The rheological behavior in solution showed that all samples exhibited lowest viscosity and a Newtonian region between 1 and 60 s−1, then this behavior changed to shear thickening. By rheological analysis in molten state was evidenced a shear-thinning behavior to these materials.

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Evaluation of the structural, thermal, rheological and morphological properties of polyethylene functionalized with a maleinized hyperbranched polyester
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Ararat Bermudez, Carlos Alberto | 2019-11-29

This experimental study was carried out with the aim of establishing and analyzing the thermal, structural, morphological, and rheological properties of a polyethylene functionalized with a maleinized hyperbranched polyester. This area of study has scarcely been reported. It is important to study the properties of this material, since it can be employed as functionalizing agent in blends of low density polyethylene and hydrophilic polymers. In addition, it also may be used as alternative for replacing the importation of polyethylene functionalized with maleic anhydride in our country. Therefore, in this experimental study, dicumyl peroxide was utilized to catalyze a functionalization reaction between low density polyethylene and maleinized hyperbranched polyester. In the experiment, dicumyl peroxide concentrations were maintained at 0.50 wt%, 1.0 wt%, 1.5 wt%, and 2.0 wt%. The resultant material after of the functionalization was characterized by various analytic methods including infrared analysis, contact angle, thermogravimetric analysis, X ray diffraction, rheological analysis and scanning electronic microscopy. The functionalization degree of the polyethylene functionalized with a maleinized hyperbranched increased with the dicumyl peroxide amount and in all cases it was higher than 8 weight percent.

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Functionalization in solution of polypropylene with a maleinized hyperbranched polyol polyester: Structural, thermal, rheological, and mechanical properties
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Nova, María | 2018-07-18

The functionalization of polypropylene (PP) with a maleinized hyperbranched polyester polyol (MHBP) was performed in solution to obtain PP-g-MHBPs. The degree of functionalization (FD) increased with MHBP and dicumyl peroxide (DCP) contents, but the contact angle followed an opposite behavior. The sample obtained with the proportion of 9.0 wt % MHBP and 2.0 wt % DCP and presented the highest FD value. An FD value of 2.4 wt %, produced a reduction of 19° on the contact angle. It was observed by differential scanning calorimetry (DSC) that the PP-g-MHBPs obtained by employing 3.0 wt % of MHBP, exhibited a slight reduction of the melting temperature (Tm) with the increase in the amounts of FD and DCP. Some FD values obtained in this study are higher than those obtained both commercial and noncommercial grades of PP functionalized with maleic anhydride. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46932.

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HYPERBRANCHED ALKYD RESINS OBTAINED FROM A HYPERBRANCHED POLYESTER POLYOL OF THE FIFTH GENERATION AND TALL OIL FATTY ACID
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Murillo Ruiz, Edwin Alberto | 2023-09

The first aim of this study was to synthesize hyperbranched alkyd resins from tall oil fatty acids and a hyperbranched polyester polyol via an esterification reaction. The second aim was to evaluate the effect of the fatty acid proportion on the properties of the resins. The modification percentage of the hyperbranched polyester polyol was between 47.68 and 66.02%. Infrared analysis shows that the alkyd resins decreased the intensity of the OH group's vibration. This decrease depends on the amount of TOFA used. Thermogravimetric and differential scanning calorimetry analyses showed that the modification of the hyperbranched polyester improved the thermal stability and the mobility of the macromolecules of the alkyd resins respectively. The viscosity of the alkyd resins was less than 10 Pa.s. They exhibited Newtonian behavior and had the highest gloss values at 60° (between 90.1 and 91.6).

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Hyperbranched polyester polyol modified with polylactic acid as a compatibilizer for plasticized tapioca starch/polylactic acid blends
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Murillo Ruiz, Edwin Alberto | 2018-03-15

A hyperbranched polyester polyol of the second generation (HBP2) was modified with polylactic acid (HBP2-g-PLA) and employed as a compatibilizer for plasticized tapioca starch (TPS)/polylactic acid (PLA) blends. The effect of the compatibilizer HBP2- g-PLA was evaluated in comparison to the control sample (TPS/PLA blend without HBP2-g-PLA). The torque value of the TPS/PLA blends with HBP2- g-PLA was lower than that of the control sample, while thermal stability and crystallinity followed opposite behavior. The glass transition temperature (Tg) and degree of crystallinity of the TPS/PLA blends with HBP2-g-PLA decreased with increasing mass fraction of HBP2-g-PLA. By scanning electron microscopy (SEM), it was observed that the morphology of the TPS/PLA blends with HBP2-g -PLA was more homogeneous than that of the control sample, confirming that HBP2- g-PLA acted as a compatibilizer and plasticizing agent to the TPS/PLA blends. Rheological analysis of the compatibilized TPS/PLA blends indicated the presence of microstructure.

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Hyperbranched polyester polyol plasticized tapioca starch/low density polyethylene blends
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Guzman, Manuel | 2017

In this work, low density polyethylene (LDPE)/plasticized starch (TPS) blends were prepared. The TPS employed in this study was obtained by plasticization of tapioca starch with a hyperbranched polyester polyol. Differential scanning calorimetry analysis showed that the melting temperature increased with the TPS content. The opposite effect was exhibited in the crystallization temperature and additional changes were not observed during the heating. X-ray diffraction analysis showed a reduction in intensity of the peak at Bragg’s angle 17.5°, proving a diminution on A type crystallinity with the increasing amount of LDPE. Micrographs obtained by scanning electron microscopy exhibited starch granules without destructure. TPS acted as a filler to LDPE, since the mechanical properties (Young’s modulus and tensile strength) improved ostensibly. The Young’ modulus and tensile strength decreased with the amount of LDPE, however, the elongation at break exhibited an opposite behavior.

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Influence of the H2O content and the time on the formation of nanostructures in a chemical solution of H2O/HF/NH4F/EG
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Raba, Angela | 2018-12-07

The influence of anodizing time on the length, morphology and photoelectrochem-ical properties of TiO2 Nanotubes has been investigated. An optimum anodizing time of 20 min at 20V leads to 220nm long of the nanotubes. By having a detailed control of the electric current one can know exactly the time in which the nanotubes grew and the time in which the process stopped. The FEG-SEM measures show the morphology of the nanotubes and how they come to separate and fall after a certain time. However, the growth of these, is uniform with little remaining material on the surface. For the solution of the anodizing process it is very important to control the amount of water, ethylene glycol and hydrofluoric acid. Small modifications in the solution change the growth time and size of the nanotubes.

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Maleinized Hyperbranched Polyol Polyester: Effect of the Content of Maleic Anhydride in the Structural, Thermal and Rheological Properties
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Ararat, Carlos A. | 2019-03-29

The aim of this work is to obtain the material that, in the future, may become a better alternative, as a functionalizing agent, to maleic anhydride (MA), or a crosslinking agent with the least amount of functional groups. To achieve that goal, a hyperbranched polyester polyol (HBP) of the second generation (HBP2G) was modified with MA to obtain HBP2GMA. The effects of the proportion of MA in the structural, thermal, and rheological properties of the HBP2GMAs were evaluated. Furthermore, these properties were compared with those of the HBP2G. A reduction in the intensity of peak corresponding to the OH stretching of HBP2G was observed with the increase in the extent of HBP2G modification by the analysis of the infrared (IR). HBP2GMAs showed a peak at 3030 cm-1 in their IR spectra, which was due to the -CH=CH- stretching of MA. This was further assessed by 1H NMR analysis. The number of MA units grafted into HBP2G was between 4 and 9, indicating a high degree of functionality. All materials possessed viscosity values below 34.94 Pa·s at 110 °C, which were dependent on the grade of the modification percentage (MP) and the molar content of MA grafted into HBP2G. Mass spectrometry analysis demonstrated the formation of products by the esterification reaction between the HBP2G and MA. The thermal stability of the HBP2GMAs determined as the decomposition temperature (Td) was between 258 and 281 °C which was better than that of the HBP2G.

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Mn-modification effects on Nb2O5 structural, optical and vibrational properties
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Raba, Angela | 2017-12-29

In this study Mn-modification (at 1%, 2.5%, 5% and 10%) on Nb2O5 was carried out through the Pechini method; the annealing temperatures: 400°C, 500°C, 600°C and 700°C, were used to study the thermal stability of the system and the crystalline growth. The crystallization at high temperatures has been investigated because low annealing temperature cannot improve the crystallization and the effect of Mn-modification concentration is worthy of a further investigation. Before annealing the samples were analysed by TGA. The structural analysis through XRD is carried out to study a possible increase of the crystallite size (L) by increasing the Mn concentration; for the samples at 700°C and 1% and 2.5% concentrations, L is increased from 39.81 to 46.45nm while L changes from 32.67 to 35.63 with 5% and 10%, respectively. After Mn-modification the evolution of (100) and (180) peaks Nb2O5 was observed suggesting that they were well defined only until 2.5%. IR and Raman spectroscopies allowed to analyse vibrational modes present in the samples: the IR spectrums for the samples at 400°C, 500°C and 600°C showed a band around 1100cm-1 which can be associated to C-C(νC-C) and C-O(νC-O) vibrations; at 700°C the shoulder was distinguished around 750cm-1 characteristics of the Nb2O5 orthorhombic structure. Vibration modes associated with Nb2O5 were found with the Raman spectroscopy; these become less intense after Mn-modification. The band gap energy was obtained through UV-Vis spectrophotometry which revealed a slight increase at 700°C.

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Niobium Pentoxide Samples with Addition of Manganese at Different Concentrations and Calcination Temperatures Applied in the Photocatalytic Degradation of Rhodamine B
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Raba, Angela | 2020-06-21

In order to improve the photocatalytic effect of Nb2O5, manganese from 1% to 10% was added by the polymeric precursor’s method. The samples obtained were subjected to different calcination temperatures from 400 to 700 °C. Characterization of the synthesized materials was performed by XRD, IR, Raman and Diffuse Reflectance Spectroscopy (DRS) spectroscopy, FE-SEM, Brunauer–Emmett–Teller (BET) method, Photoluminescence (PL) and Dynamic Light Scattering (DLS). Photocatalytic performance for degradation of Rhodamine B was also evaluated. The Rietveld refined X-Ray Diffraction (XRD) pattern of Nb2O5:Mn 1.0 wt.% (700 °C) sample was similar to that of the un-doped oxide, therefore indicating that Nb was replaced by Mn and, consequently, there are not significant variations in the oxide structure. The Nb2O5:Mn 10.0 wt.% (700 °C) sample has the lowest band gap energy. The specific surface area (SBET) PL value increased as manganese concentration increased. The Nb2O5:Mn 5.0 wt.% (700 °C) sample has an Eg of 3.15 eV and morphological and surface characteristics that made it an appropriate photocatalyst in the Rhodamine B degradation. The novelty of this work relies on the use of a small quantity of Mn ions as dopants leading to Nb2O5:Mn nanostructured particles without using any surfactant or other additives

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Polietileno de baja densidad funcionalizado con un poliéster poliol altamente ramificado maleinizado
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Murillo, Edwin A. | 2016-02-22

En este trabajo, polietileno de baja densidad (PEBD) fue modificado en estado fundido con un poliester poliol altamente ramificado maleinizado (HBPAM), usando varias proporciones de peróxido de dicumilo (0.5, 1.0, 1.5 y 2.0 %). El análisis infrarrojo mostró las señales de grupos OH, C=O, -COOR y -C=C- del HBPAM en el espectro de las muestras funcionalizadas (PEBD-g-HBPAM). El grado de injerto (GI) fue entre 9.14 y 9.82 %. El índice de fluidez de las muestras PEBD-g-HBPAM fue más bajo que el del PEBD, y no exhibió una dependencia con el contenido de peróxido de dicumilo y GI. Excepto para la muestra obtenida con un 2.0 % de peróxido de dicumilo, todas las temperaturas de fusión de las muestras de PEBD-g-HBPAM fueron similares a la del PEBD. La entalpia de fusión de las muestras de PEBD-g-HBPAM disminuyó con la concentración de peróxido de dicumilo y GI. El módulo ténsil de estas muestras fue más alto que el del PEBD, pero la elongación a la ruptura fue más baja

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